Seismic Response Analysis of Portal Water Injection Sheet Pile

Journal of Ocean University of China (Ocean and Coastal Sea Research)ISSN 1672-5182, January 30, 2007, Vol.6. No.1, pp.90-94http://www. ouc.edu.cn/xbywbE-mail:xbywb@ouc.edu.cnSeismic Response Analysis of Portal WaterInjection Sheet PileWANG Yuanbin, GUO Haiyan' , and ZHANG ChunhuiCollege of Engineering, Ocean University of China, Qingdao 266071, P. R.China( Received September 20, 2005; accepted May 29, 2006 )Abstract To further the study on the newly developed portal water injection sheet pile under static loads, in this paper, by adoptingthe nonlinear calculation module of FEM software ANSYS, a model for the interaction between the soil and the sheet piles is set up,and the seismic response analysis for this type of space-retaining structure is performed. The effects of the embedded depth and thedistance between the front pile and the back pile on the dynamic characteristics of the portal water injection sheet pile are studied.Key words portal water injection sheet pile; ANSYS software; nonlinear finite element analysis; dynamic interaction; seismicresponseDOI 10.1007/ s11802-007-0090-xbefore. As the portal water injection sheet pile is chiflyused in building engineering and hydraulic engineering,1 Introductionits safety is of extreme importance.The portal water injection sheet pile (PWISP) is a newtype of space-retaining structure developed for the7777777777Shengli Oil Company. It was developed based on theBent capSoilcombination of the practical needs of hydraulic projectsand the technical principle of jet-drilling in the oil indus-|Soiltry and has been successfully used for disaster preventionand hydraulic projects (Guo, 2002, 2005). It consists ofthe double-row parallel-prefabricated reinforced concrete777777777sheet piles and the connection bent cap on top of the piles(Fig.1). Its primary technique is to directionally jet andsplit the stratum with high pressure water and at the sametime to insert the sheet piles into the stratum under theFront row pile Back row pilecontrol of the directional devices, and then to connect thetwo rows of independent sheet piles together to form aFig.1 Portal water injection sheet pile.dike or other construction with a series of special methods.In contrast with the traditional piles, the portal water in-This paper establishes a finite element model for thejection sheet pile has many advantages, such as high pre- interaction between the soil and the sheet piles and per-fabrication and rapid construction, low cost, and good forms a seismic response analysis for the portal watercapability of erosion resistance. Therefore, it has broad injection sheet pile adopting the nonlinear calculationprospects for engineering applications.module of finite element software ANSYS.The portal water injection sheet pile under work condi-tions is mainly subject to static and dynamic loads. For2 Dynamic Nonlinear Interaction Betweenstatic loads, its design and calculation mainly follows themethod for double-row piles in pit excavation, and somethe Soil and the Sheet Pilespositive results (Cai, 1997; Zheng, 2004; Zhou, 2005)There exist two kinds nf nnlinearitv hetween the soilhave been achieved. However, its dynamic characteristicsand the sheet pil中国煤化工fthe soil ma- .and response under seismic loads have never been studiedterial, which h;HCNMH G researchers(Zheng, 2002). In this paper, the Drucker- Prager model* Corresponding author. E-mail: hyguo@ouc.edu.cn(Manual of ANSYS, 2000) is adopted to consider the in-.Wang Y. B. et al: Seismic Response Analysis of Portal Water Injection Sheet Pile91fluence of this kind of nonlinearity. The other is the relative flow rule is adopted. As the yield surface is in-nonlinear state caused by the interaction between the soil variant when the soil gradually yields, there is no harden-and the sheet piles. The soil and the reinforced concrete ing phase.sheet piles widely differ in property. The continuity of thedisplacerment exists only under certain stress level on the 2.3 Contact Elementinterface between the soil and the sheet piles, beyondSuppose there is contact between object A and object B,which slippage and separation are certain to occur. Inthe equation of the entire system can be written asorder to simulate this characteristic, a number of contactelements are used in this paper to reflect the slippage and「Ky 0 ][asL JFal=0,(5separation.0 Kg]\ag」 Fg2.1 Motion Equation of Interaction SystemwhereK A andKp are the contact stiffness of A and B,According to the current dynamic finite element respectively; axa andap are the contact nodal displace-method, the nodal displacement{u}, velocity{i}, and ments of A and B, respectively; andFandFg are theacceleration {i} are regarded as unknown variables, then nodal forces caused by external loads, respectively.the governing motion equation for the dynamic responseThe objects A and B are linked by two nodal restrictionof a system in the finite element formulation can be ex- elements. As a result, the nodes with independent conju-pressed asgated local displacements are defined at the joints, andthe internal force work and external force work are equal:[M]{i}+[C]{i}+[K]{u}={F"}=-[M]{ig}，(1)A.,a +A,x=Ae,a +Az,i,(6)where [M], [C] and [K] are the mass matrix, dampingA.a =δ{a}' {},(7)matrix and stifnesss matrix, respectively, {F}is thevector of the nodal loads, and{ig }is the vector of the4.2 =δ{z}" {[c]{a}},(8)nodal acceleration.Aoa=δ{a} {F},2.2 Nonlinear Model of the SoilAex=8{A}" {a,},Soil is grainy; and the stress-strain curve of the soilappears nonlinear even at the beginning of loading. In- where A a is the virtual work of the nodal internal force,creasing the loads will lead to yielding and soil flowing. A, ais the virtual work of the additional nodal internal .Finally the soil collapses. Therefore, the study of the soil force caused by external loads, A.a is the work of thenonlinearity includes yield criterion, failure criterion and nodal external force, Ae,xis the work of the additionalflow rule (Manual of ANSYS 2000; Zheng, 2002).nodal external force caused by external loads, a and a,In this paper, Drucker-Prager's yield criterion, which is are the nodal displacement and initial displacement, rean approximation to the Mohr-Coulomb criterion (Zheng，spectively, 入and F are the interaction force between2002), is adopted, and can be written asnodes and the nodal force caused by the external force,respectively, and [C] is the transition matrix from elementF=σe -σ, =3βσ +stiffiness matrix to system stiffness matrix.(2)The element stiffness matrix of the restricting nodes6C cos φcan then be written as follows:[s$'M[s]√3(3- sinq)) [c]" ]fa\_ JF(11)σ。=3βσm +[o"TMIsg,(3)[c] 0 ]la,j lajWith the loads increasing, the interaction of the soil6C cosφ0)- V3(3-sino)'’(4) with the piles is simulated step by step. At the beginningof the calculation, a contact state (fixation, slippage,whereσ。is the equivalent stress, σm =(1/3)4,is the stretch, etc.) of the contact elements is assumed. Based onfirst stress invariant, {S} is the deviatoric stress, β is thethe assumed state, the matrix of the total stiffness and thematerial constant, [M] is the directions transformationvector of equivalent loads are calculated. A group of solu-matrix of yielding stress, σ, is the yield parameter of thetions are obtained by solving the finite element equations,“中国煤化工f the contetsoil, C is the cohesion of the soil, andφ is the internal state does not aEntact state, afriction angle.new contact statdYHCNMHGroftheloadsThe flow rule defines the development of the plastic is modified. The iteration proceeds until the results con-strain with the yielding. In the Drucker-Prager model, verge..92Journal of Ocean University of ChinaVol.6, No.1, 2007the sheet piles (Contact 172 and Target 169 in ANSYS)3 Finite Element Calculation Model ofThe contact elements are automatically generated ac-cording to the grid plot and node positions of the soil andANSYSthe sheet piles. The finite element model and its size areNormally, the portal water injectin sheet pile is still in shown in Fig.2.a linear-elastic stage under work conditions when the soilIf the calculation domain is sufficiently large, the in-enters into the yielding state. Therefore, the sheet pilesfluence of the boundary conditions can be neglected. Inare regarded as linear-elastic material, and the soil is re- our calculation, a 60m x 30m calculation domain is ac-garded as elastic plastic material simulated by the Dru-cepted to guarantee the negligible influence from thecker-Prager model. Eight-node isoparametric elements areboundary conditions and the boundary conditions areused to set up the calculation model for the soil and the chosen as fsheet piles. The sie of the soil element is 0.3mx0.3m，pdisplacements are zero， Lateral boundaries: theand that of the sheet pile element is 0.15mx0.15m. .x-displacements are zero. The sheet piles are restricted byTo acratly siulate the sippe betwen the sheet the soil, and the strengh of the rstricion is deteminedpiles and the soil, face-face flexibility -rigidity contactby the magnitudes of the normal and tangent contactelements are applied on the interface between the soil and siffnesses.sExcavation depthB= 60mFig.2 Finite element model.bedded depth is set to 6 m and the distances between thefront pile and back pile are 1.5 m, 2 m, and 3 m, respec-4 Calculation and Analysistively. It is found that the distance between the front pileTo analyze the static/dynamic characteristics and the and the back pile has a marked effect on the displacementeffects of the parameters such as the embedded depth on of the top point A.the characteristics, a simplified case is obtained fromThen the distance between the front pile and the backseveral practical projects of the Shengli Oil Company. pile is set to be 2 m, and the embedded depths are 4m, 5m,The parameters of the study case are given in Tablel.and 6m, respectively. It is found that the displacements ofthe top point A are 5.23 cm, 4.4 cm, and 4.0 cm, respec-4.1 Static Analysistively. It can be seen that the displacement of the point AFirst, the static responses are calculated when the em-markedly decreases with increasing embedment depth.Table 1 Calculation parametersSoil parameterValueSheet pile parameterYoung's modulus5x I0'kPa6x10'kPaPoisson's ratio0.40Density1800kg m32500 kg m3Internal friction angle30°Length12mCohesion30kPaThe friction cofficient of contact element is 0.3incident wave p中国煤化工nd the maxi-4.2 Dynamic Analysismum acceleratiol:OH.CNMHGsponseoftheThe EI-Centro seismic wave is selected as the external portal water injecuon sneet pue Is inen analyzed.seismic loads on the portal water injection sheet pile. TheFirst, the seismic responses are calculated when the.Wang Y. B. et al: Seismic Response Analysis of Portal Water Injection Sheet Pile93distances between the front pile and back pile are l.5m, 2the distance between the front pile and the back pile hasm, and 3 m, respectively, while the embedded depth is 6m. ltte effects on the dynamic responses.The history curves of the additional displacement andThen, when the pile distance is 2m, and the embeddedacceleration at the top point A are shown in Figs.3, 4 and depths are 4m, 5m, and 6 m,respectively, the history5, respectively. It can be seen that the displacement of the curves of the additional displacement and acceleration oftop point A can reach up to 3.3 cm. At the same time, the the top point A are shown in Figs.7, 6 and 4, respectively.acceleration is remarkably magnified, too. The amplitude It can be seen that both additional displacement and ac-of the acceleration is twice that of the incident wave. Dif- celeration of the top point A slowly increase with de-ferent from the situation under static loads, the change of creasing embedded depth.0.040.032030.0.73435 g.03-公0..02 t0.4-.01+复0.0.000.0-- 0.01-0.2--0.02的-0.4..0.03.-0.- 0.04+-0.810Time (s)Fig3 History curves of displacement and acceleration when the embedded depth is6m and the distance is 1.5m.0.04.0.8.0.0331700.74255g0.03命0.0.4会0.2日0.0-0.01-0.03 .-0.0480Time (S)Time (8)Fig.4 History curves of displacement and acceleration when the embedded depth is6m and the distance is 2 m.0.04-0.0330760.73972g@ 0.60.02g 0..01 t鲁0.g -0.0.0F在基。-0.4-0.03-0.04+i。 -0.846ime (s)Fig.5 History curves of displacement and acceleration when the embedded depth is6m and the distance is 3 m.0.04 .0.0355010.75446g.0.6[ 0.有0.0.00V-MAA -0.4.03 +中国煤化工MHCNMH GFig.6 History curves of displacement and acceleration when the embedded depth is5m and the distance is 2m..94Journal of Ocean University of ChinaVol.6, No.1, 20070.04..8 T0.0390610.75463 g0.03.6+且o.c| O 0.4-0.2+0.01MMMMI-0.00Arfom t0.2 t- 0.01A -0.02 .-0.6 7.032810-0.8-4Time (s)Fig.7 History curves of displacement and aceleration when the embedded depth is4m and the distance is 2 m.structure of double piles in soft clay. J. Zhejiang Univ. Sci,20 (4): 65-71 (in Chinese).5 ConclusionsGuo, H. Y., F. R. He, D. F. Liu and Y. Luo, 2002. Techniques(1) The additional displacement at the top A of theand Applications of Water Injection Sheet Piles. 2002 Inter-sheet pile caused by seismic loads is large, and can reachnational Symposium on Safety Science and Technology. Bei-jing, Sci, (3): 436-441.up to 3.3cm in the study case. The amplitude of the ac-Guo, H. Y, Q. Shun, L. Y. Liu, and Y. B. Wang, 2005. Stabilityceleration is also remarkably magnified, which can beAnalysis Against Slide of the Portal Water Injection Sheettwice that of the incident wave. However, as is differentPile. J. Ocean Univ. Chin, 35 (6): 1053- 1056 (in Chinese).from the situation of static analysis, the embedded depthManual of ANSYS, 2000. ANSYS Incorporation. Pittsburgh, U.and the pile distance have lttle effect on the dynamic s. A.1054-1148.responses.Zheng, G, X. Li, C. Liu, and X. F. Gao, 2004. Analysis of Dou-(2) Under seismic loads, with the decrease of the em-ble-row Piles in Consideration of the Pile-soil Interaction. J.bedded depth of the PWISP, the top displacement andacceleration increase. However, the increments are very Zheng, Y. R.,Z. J Shen, and x. N. Gong, 2002. Plastic Me-small, which is quite different from the case of staticchanics Principle of Rock and Soil. Chinese Architecture In-dustry Publishing, Beijing, 112-142 (in Chinese).loads.Zhou, C. Y., Z. Q. Liu, W. Shang, H. Chen, andS. Y. Wen, 2005.A new mode for calculation of portal double row anti- slidingReferencespiles. J.Rock and Soil Mechanics, 26 (3): 441-444 (in Chi-Cai, Y.Q, Y. Q. Zhao, s. M. Wu, Y. M. Chen, and x. Y. Tang,nese).1997. FEM analysis of the deep pit excavation with retaining中国煤化工YHCNMH G.